To support registration of instances, we add additional syntax to their definition.
为了支持实例的注册，我们在它们的定义中添加了额外的语法。
2
This specification also contains the definition of the correct syntax of the input and output messages.
此规范还包含输入和输出消息的正确语法的定义。
3
A joint use of both features facilitates the definition of new statements without extending the syntax and without using macro-like meta-programming facilities.